German researchers are developing a long-lasting battery by teaming up four German universities, two research institutes and two companies. They aim to increase the amount of energy from wind and solar power sources that can be stored by redox flow batteries and integrate it smoothly into the electricity grid.
The Federal Research Ministry is subsidizing the project with 5 million Euros a year for the next five years. The joint research project called TubulAir is being funded by the Federal Ministry of Education and Research over a project period of five years.
The target of TubulAir is the development of a Tubular Vanadium Air Redox Flow Battery which is capable of storing vast amounts of electrical energy in a cheap and energy efficient manner.
In 1973, first investigations were undertaken by NASA to examine the feasibility and potential of Redox Flow Batteries (RFB) for large stationary energy storages . In 1976, a patent describing the characteristics of the NASA developed Redox Flow Battery, comprising two completely solved redox couples , was registered. Since the 1980s, a RFB has been developed by M. Skyllas-Kazacos et al., which utilizes solely dissolved Vanadium in four oxidation stages. By this approach, the issue of degradation caused by cross-contamination, which caused the developments of the NASA system to be given up, could be avoided.
Within the last decades, in Australia, Japan, the US, China and Europe RFB’s with different redox couples have been developed. The potential of the All Vanadium Redox Flow Battery for stationary storage of electric energy has been shown since the 1990s in various demonstrational and pilot plants in the range from kW/kWh to MW/MWh .
By detaching the cell and the electrolyte storage, RFB offer interesting and cost-effective solutions for energy storages with simple scalability, high endurance and an excellent efficiency.
Main target of the joint research project is the development of the key technologies for the cost-effective manufacturing of a micro tubular redox flow battery with increased energy and power density for stationary appliances. The suitability of planar All Vanadium Redox Flow Batteries (VRB) for this purpose has been shown in various demonstrational projects. The comparatively low energy density of the VRB as well as the cost intensive manufacturing of planar cell stacks require significant improvements as a prerequisite for a broad market entrance. To achieve these goals, in this project the fluid electrolyte of the VRB on the cathode shall be replaced by an air/water steam electrode. Thus the energy density might basically be doubled compared to a VRB. To achieve a better cost effectiveness, a micro tubular cell structure will be developed.